1. Field of the Invention
The present invention relates to a high-output tunnel magnetic resistance device with a high thermal stability, and to a low-power-consumption nonvolatile magnetic memory using the same.
2. Description of the Related Art
A tunnel magnetic resistance device using magnesium oxide as an insulating film disclosed in S. Yuasa. et al., Nature Material 3, 868 (2004), is a tunnel magnetic resistance device that is applied to a highly-integrated magnetic memory in the future, because, with the disclosed device, a magnetoresistance ratio that is several times larger than that with a tunnel magnetic resistance device using Al oxide as an insulator described in T. Miyazaki and N. Tezuka, J. Magn. Magn. Mater. 139, L231 (1995) is obtained. A conventional nonvolatile magnetic memory is made up of memory cells in each of which a tunnel magnetic resistance device is formed on a MOSFET. MOSFETs are used for switching operations to energize the bit lines and the word lines. Storing data is accomplished by rotating the magnetization direction in the tunnel magnetic resistance device by using a current-induced spatial magnetic field generated by the energization. Recalling data is accomplished using the output voltage of the tunnel magnetic resistance device. Beside the method in which the above-mentioned magnetization rotation using the current-induced spatial magnetic-field, a spin transfer torque magnetization reversal method, known as a method to achieve the above-mentioned purpose, is disclosed, for example, in the specification of U.S. Pat. No. 5,695,864, or in Japanese Patent Application Laid-open No. 2002-305337. Such a method is also known as a spin injection magnetization reversal method, in which magnetization rotation is accomplished by passing a current directly through the magnetic resistance element. To a tunnel magnetic resistance device disclosed in Japanese Patent Application Laid-open No. 2005-294376, a free layer in which a plurality of ferromagnetic films are stacked with a non-magnetic film interposed in between is applied for the purpose of achieving a stable spin transfer torque magnetization reversal operation against the penetration of an external magnetic field.